DESCRIPTION (From applicant's proposal): The main theme of the proposed research is to increase our knowledge of the human middle ear and cochlea based upon the use of acoustic response testing in the ear canal. Such tests are inherently noninvasive so that it is hoped that the knowledge gained on basic mechanisms in hearing will have significance for clinical utilization. The first aim is to examine new forms of otoacoustic emissions (OAE), which will provide a clearer understanding of mechanical processes on the basilar membrane. Time-frequency representations of OAE transients will delineate the fine structure of the tonotopically organized cochlear dynamics, which is otherwise partially obscured by conventional waveform or spectral representations. The second aim is to assess middle-ear and cochlear mechanisms in an integrated manner using a power-transfer approach. Such an approach will combine aspects of wideband tympanometry, otoreflectance and OAE measurements to interpret power flow from the ear canal through the middle ear to the cochlea, and back. The third aim will apply these new types and representations of OAEs and the power-transfer approach in large-scale studies of normal ears, and ears with middle-ear and cochlear impairments. The goal is to improve techniques to predict conductive, cochlear and mixed hearing losses, and to better understand how acoustic response variables can be combined, for example, across frequency or static pressure in the ear canal, in order to understand the underlying cochlear and middle-ear mechanics and coupling in normal and impaired ears. The results of the proposed experiments will provide useful data for theoretical modeling of the auditory periphery, and could significantly improve our ability to identify persons with conductive or cochlear hearing loss.